It's been a long time since I've looked at one of the dealer-install units. My fuzzy memory tells me that the lower unit is more correct, but the part number will tell you which is the older unit. The higher the part number, the newer the part. Many parts from the early '70s are tagged with numbers starting at about 346 or so. Comparing part numbers from similar parts over a number of years, will get you an excellent idea of the correct order and starting numbers to look for in one of these add-on units. The upper unit looks like a late-'70s or early-'80s one, possibly from a van. That's just the results from my memory, and dust-bunnies in there might have skewed the results.
